Treatment of brine.



G. W. MALCOLM & F. T. MUNTON.

TREATMENT OF BRINE.

APPLICATION FILED OCT. 26, 1908.

1 030 103 Patented June 18, 1912.

enoncnw. MALCOLM, 0F navnmim, AND FREDERICK 'r. MUNTON, or wnvsroan,

ENGLAND, ASSIGNORS TO THE SALT UNION LIMITED, OF LIVERPOOL, ENGLAND.

TREATMENT OF BBINE.

Specification of Letters latent.

Patented June 18, i912.

Application filed October 26, 1908. Serial No. 459,564.

useful Improvements in or Relating to the- Treatmcnt of Brine, of whichthe following is a specification.

This invention relates to the manufacture of salt from natural brine bythe vacuum process of evaporation and has particular reference to aprocess in which the calcium and magnesium salts are removed beforeevaporation of the brine by electrolyzing the brine to form sufiicientsodium hydrate to decompose the said salts and precipitate the magnesiumand most of the calcium as hydrates and then treating the brine withcarbonic acid to complete the removal of calcium, 'the chief objectbeing to provide for the more economic production of the salt and toeffect the recovery of certain of the by products separately for use inthe arts.

According to the present invention the brine is subjected to apreliminary treatment in an eloctrolytic cell to secure the desiredalkalinity, then treated for effecting the separation of the magnesiumprecipitate, subjected to further treatment in an electrolytic cell, andfinally acted upon by gases containing carbon dioxid, which gases arepasses through the brine to form sodium carbonate and effect theprecipitation of the calcium carbonate. Further the power for drivingthe engines for working the dynamos employed in generating the currentfor use in the electrolyzing step above referred to is derived from thesteam which, at present, is used for evaporating purposes only and to asmall extent for driving the air and other pumps, which areindispensable accessories to a vacuum plant,

and the exhaust from such engines, which may be superheated, is passeddirectly to the vacuum plant to furnish the heat necessary for effectingthe evaporation of the brine.

In order that the said invention may be clearly understood and readilycarried into effect, we will proceed to describe the same more fullywith reference to the accompanying drawing in which we have representeddiagrammatically a plant adapted to accomplish the manufacture of saltaccording to this invention.

In the plant illustrated in this drawing A, A, A are steam generatorsfor producing high pressure steam which'passes, by way of the pipe B andbranch pipes b, 6,?) to the respective non-condensing engine C, C, C,the exhaust steam from these engines being conveyed by a pipe 0 to the-xevaporating pans D, D, D. The engines C, C, C, are arranged to driveelectric generators E, E, E

whereby electric current is supplied to elec-' trolyzing cells of anysuitable type such as F, F F

The current is conducted to the cells by way of the leads f f thearrangement of these leads admitting of the connection of anv one of thedynamos with vany series of cells. Brine is supplied to the cells byhand or by any other convenient means and is electrolyzed therein,caustic soda being produced. It will be seen on reference to the diagramthat the cells F are in communication, b way of a pipe g with aseparator G while t e cells F and F are in communication with anotherseparator G by way of pipes g and a branch pipe g which is common toboth the pipes g Raw brine is introduced into the cells F by the pipe 9and is there partiallyelectrolyzed. The current is so regulated thatsufiicient caustic soda is produced to precipitate all the magnesiumsalts which are separated from the brine. The clear partially purifiedbrine is now led from the separator G through the pipe 9 g, g to befurther electrolyzed 1n the cells F F In these cells sufficient causticsoda is formed to combine with the calciuin salts present in the brinewhen subjected to carbon dioxid gas. The treated brine then flows bypipes g, g, g" to the drawn ofi' from a separator G through the pipe h,or by other suitable means. The chlorin which results from theelectrolysis of the brine in the cells F, F, F may be collected by thepipes 7c and conducted by way of the pipe K to the chlorinating chambersK, K K where bleaching powder may be manufactured in the well knownmanner by absorbing the chlorin by means of lime.

It will be seen that, after the prel minary electrolysis of the brine,adapted to secure the desired alkalinity, by the hereinbefore describedfurther treatment, suitable for the purpose, the magnesium precipitateis effectually separated from the brine, and rendered available fortreatment by any convenient means whereby the same may be converted intoa commercial article further, that, by the action of the flue gases fromthe steam generators the gases being passed through the further treatedand partially purified brine, the carbon dioxid in the said gasescombines with the caustic soda formmg sodium carbonate, CELlClllIl'lcarbonate 1s precipltated and the equivalent of sodium sulfate left inthe brine solution. ,-;This latter will be found quite harmless from thepoint of view of evaporation, and, moreover, will be present in quite anegligible quantity. As a by product bleachingpowder is produced by theuse of the saturating chambers wherein the absorption by lime of thechlorin evolved from the electrolytic process is accomplished. The cycleof operations is, therefore, by means of 'the steam, to first drive theengines and the current generating plant; the exhaust steam from theengines is passed-by means of pipes or other conduits to the vacuumplant where it effects the evaporation and the making of the salt fromthe previously electrolyzed and purified brine, which is led into theevaporating pans. The resultant by products are treated in any knownmanner to convert or render the same into commercial commodities for usein the arts; thus the process may be carried on continuously and withgreat economy and profit. I

By the various steps in the above described electrolysis, the magnesiumand the calciumsalts are effectually separated in the pure state as theyare thrown down in different periods of the process. I

What We claim and desire to secure by Letters Patent of the UnitedStates is 1. In the manufacture of salt from natural brine by thevacuum" proce ss of evaporation, the herein described method of carryingon the said process continuously consisting in subjecting the brine to apreliminary treatment in an electrolytic cell so as tosecure the desiredalkalinity, separating the magnesium precipitate from the'brine,subjecting the brine to a further treatment in an electrolytic cell,passing gases containing carbon dioxid through the brine to form sodiumcarbonate and effect the precipitation of calcium salts thereby leavingthe equivalent of sodium salts in solution, and separating the purifiedbrine by exhaust steam from .the engines. l

2. The process of purifying brine consisting in electrolyzing the brineto an extent suflicient to precipitate the magnesium salts theneffecting the precipitation of the calcium salts by treating theremaining brine solution with gases containing carbon dioxid,

then conducting the purified brine to the' evaporating pans which areheated by the exhauststeam from the engines.

In the continuous process of manufacturing-salt from natural brine bythe vacuum evaporation process the method of purifying the brine andsuccessively eliminating the magnesium and calcium salts therefrom,consisting in causticizing the brine by electrolysis, separating themagnesium hydrate formed thereby, then treating the brine solution withgases containing carbon dioxid to precipitate the calcium salts, sodiumsulfate being left in solution and finally conducting the purified brineto the evaporating panswhich are heated by exhaust steam from theengines.

In testimony whereof we aflix our signatures in presence of twowitnesses.

GEO. WV. MALCOLM.

" F. T. MUNTON.

VVit-nesses CLARENCE H. WIMSHURST, RICHARD H. PHILLIPS.

